edit:Maybe would be not bad idea to set minimal order ammount to prevent "24hour change %" manipulations, which is very cheap now.

2.0019 BTS / .2224 BTSR = 9.00134892 BTS/BTSR is the price at which the second trade was executed.At a price of 8.999 BTS/BTSR you would have received 2.0019 / 8.999 = .22245805, but BTSR has only 4 decimals precision, that's why it was rounded down.Works as designed.

After the trade has happened the original orders no longer exists, only the trade as it was executed.What the "correct" price is lies in the eye of the beholder I suppose.With such low volume orders a measurable price difference due to rounding errors is to be expected. Note that the actual difference in value is around 1/1000th of a US cent.